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.. _redirection:
Redirection
===========
sh can redirect the STDOUT and STDERR of a process to many different types of
targets, using the :ref:`_out <out>` and :ref:`_err <err>` special kwargs.
Filename
--------
If a string is used, it is assumed to be a filename. The filename is opened as
"wb", meaning truncate-write and binary mode.
.. code-block:: python
import sh
sh.ifconfig(_out="/tmp/interfaces")
.. seealso:: :ref:`faq_append`
File-like Object
----------------
You may also use any object that supports ``.write(data)``, like
:class:`io.StringIO`:
.. code-block:: python
import sh
from io import StringIO
buf = StringIO()
sh.ifconfig(_out=buf)
print(buf.getvalue())
.. _red_func:
Function Callback
-----------------
A callback function may also be used as a target. The function must conform to
one of three signatures:
.. py:function:: fn(data)
:noindex:
The function takes just the chunk of data from the process.
.. py:function:: fn(data, stdin_queue)
:noindex:
In addition to the previous signature, the function also takes a
:class:`queue.Queue`, which may be used to communicate programmatically with
the process.
.. py:function:: fn(data, stdin_queue, process)
:noindex:
In addition to the previous signature, the function takes a
:class:`weakref.ref` to the :ref:`OProc <oproc_class>` object.
.. seealso:: :ref:`callbacks`
.. seealso:: :ref:`tutorial2`
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